The studens of a class take a test having 10 questions of true or false objective type questions. No two students answer are same. None of the students has got all the answers correct. How many students are there in the class.

Question

$\begin{array}{1 1} 2^{10}-1 \\ 2^9 -1 \\ 2^9 \\ 2^{10} \end{array}$